The current tendency is toward fabricating slim, compact, lightweight and high-performance electronic devices, including microphones. A microphone is used to receive sound waves and convert acoustic signals into electric signals. Microphones are widely used in daily life and are installed in such electronic products as telephones, mobiles phones, and recording pens. In a capacitive microphone, variation of acoustic pressure (i.e. local pressure deviation from the ambient atmospheric pressure caused by the sound waves) forces the diaphragm to deform correspondingly, and the deformation of the diaphragm induces a capacitance variation. The variation of acoustic pressure can thus be obtained via detecting the voltage difference caused by the capacitance variation.
This is distinct from the conventional electret condenser microphones (ECM), in which mechanical and electronic elements of micro electro-mechanical system (MEMS) microphones can be integrated on a semiconductor material using integrated circuit (IC) technology to fabricate a miniaturized microphone. MEMS microphones have advantages such as a compact size, being lightweight, and having low power consumption, and they have therefore entered the mainstream of miniaturized microphones. Furthermore, MEMS microphones can be easily integrated with a complementary metal-oxide-semiconductor (CMOS) process and other audio electronic devices.
Although existing microphone devices have generally been adequate for their intended purposes, they have not been entirely satisfactory in all respects.